1. Field of the Invention
The present invention relates to a low cost Continuous Positive Airway Pressure (CPAP) device used to treat sleep disordered breathing (SDB) conditions such as Obstructive Sleep Apnea (OSA). In particular, the present invention relates to a low cost CPAP flow generator and humidifier assembly.
2. Background of the Invention
Since Sullivan's invention of nasal CPAP treatment of “snoring sickness”, treatment systems have become quieter and more comfortable for patients. Typically, a patient is tested by a sleep physician who titrates a treatment pressure for the patient, and the patient is sent home with a basic low-cost CPAP device that is set to, and remains at, that treatment pressure. While more sophisticated devices exist that can to some extent automatically titrate, the majority of patients are treated with a basic low-cost CPAP device. A basic CPAP device comprises a blower that can provide a supply of air or breathable gas at pressures in the range of 4 cmH2O to 20 cmH2O. There is a constant need in the art to reduce cost while providing the same functionality.
A common configuration of a treatment system comprises a CPAP device and a patient interface, typically a nasal mask. The nasal mask forms a sealing interface with the patient's nasal passages in use so that the supply of air at positive pressure from the CPAP device is delivered to the patient's airways. While the patient is wearing a nasal mask, their mouth is uncovered.
In some situations, patients “mouth breath” during sleep. When this happens while wearing only a nasal mask, air can pass in the mask and straight out the mouth. This can lead to drying of the airway and patient discomfort. This patient discomfort can to some extent be alleviated by the use of a humidifier placed between the CPAP device and patient interface.
Many humidifiers are available, although the most convenient form is one that is either integrated with or configured to be coupled to the relevant CPAP device. While passive humidifiers can provide some relief, generally a heated humidifier is required to provide sufficient moisture to the air so that patients will be comfortable. Humidifiers typically comprise a water tub having a capacity of several hundred milliliters, a heating element, a control to enable the level of humidification to be varied, an air inlet to receive air from the blower, and an air outlet adapted to be connected to an air delivery conduit so that the humidified pressurized air may be passed to the patient interface. Usually, the water tub is removable from the system so that it can be refilled when necessary.
Often patients may start with a CPAP flow generator/blower and later desire to include a humidifier. However, not all patients require humidification. Thus there is a commercial advantage in having a system that allows a patient to start with a flow generator and later choose to upgrade to a humidifier at low cost.
The cost of producing equipment is influenced by a number of factors including parts, labor, factory overhead, packaging, transport, and distribution costs and taxes. Labor costs can be reduced in a number of ways, such as by designing for simple, low cost manufacture. For example, a design that calls for fewer parts is quicker, simpler and cheaper to manufacture. A design that uses cheaper parts is likewise cheaper overall.
There is a spectrum of humidifier/CPAP device coupling configurations from fully integrated to completely separate. In between these end points, there is a range of intermediate configurations.
Moreover, peripheral components such as a humidifier can be more expensive since they typically include hardware and other expensive components and controls which are necessary for communication with the basic CPAP device.
By way of example, in a completely separate configuration there is only a hose delivering a supply of air at positive pressure between the CPAP device and humidifier, and there are no electrical signals between the two devices, such as control or sensing signals. While the CPAP device might be able to discriminate the presence of the humidifier by an increase air impedance on the hose, there is no signal sent between the two devices to advise the CPAP device of the presence of the humidifier. Furthermore, all heating and humidification controls reside on the humidifier. Power must be separately supplied to the humidifier. An example of such a humidifier is the ResMed HUMIDAIRE™ humidifier.
An example of a system using an intermediate configuration is ResMed's S7 CPAP device. In this system, the CPAP device can be used without any humidifier. However, if the front panel of the CPAP device is removed, a specific humidifier, e.g., the ResMed H2i™ humidifier, may be connected. There are a number of electrical and mechanical connections between the CPAP device and humidifier. Power for the heater is supplied from the CPAP device and hence there is no separate power cord for the humidifier. Humidification controls reside on the humidifier.
In a fully integrated system, the humidifier is not removable from the CPAP device (although the humidifier tub may be removable to facilitate refilling).
Other known systems include Fisher & Paykel's PCT Application no. WO2004/043528 and Respironics' RemStar AUTO product.
In summary, there is a need in the art to provide a basic low-cost CPAP device which is upgradeable with a suitable humidifier.